The Celtic faithful have hailed new Bhoy Robbie Keane as a Messiah, signed to solve all their problems.

His stunning deadline-day capture just hours before the latest transfer window slammed shut generated newspaper headlines throughout Britain. But his fairytale story turned a little sour at a frosty Rugby Park when Kilmarnock stole Keane's thunder by shocking the Hoops and placing a huge dent in their championship challenge.

In fact it was another loan star in Chris Maguire, who moved south from Aberdeen to the Ayrshire men, who upstaged the Irishman by netting the winning goal. And now the dust has settled on the latest transfer moves in Scotland, just who has landed the best deals?

That could well become apparent when many of the other new January signings get their opportunities to shine in this weekend's Scottish Cup.

Tony Mowbray, who has made sweeping changes to the Celtic squad, now knows he faces a real fight if he is going to wrestle back the SPL title as they trail rivals Rangers by ten points and no longer have a game in hand.

Hence the arrival of Keane on loan and he has been charged with the task of breathing new life into Celtic's stuttering challenge.

Perhaps the Parkhead manager may now feel Celtic's best chance of silverware lies in the Scottish Cup with his troops facing a tricky trip to Dunfermline on Sunday. Maybe Keane will find his feet in Fife and certainly all eyes will again be on the Irishman who is reportedly set to earn a handsome fee from his short-term spell in Glasgow.

East End Park follows quickly on from the nightmare trip to Ayrshire and both grounds will seem like a world away for the Tottenham Hotspur striker who is used to gracing the likes of Old Trafford and Stamford Bridge.

Keane, 29, is a much-travelled striker having served Wolves, Coventry, Inter Milan, Leeds United, Tottenham twice and of course also had an unsuccessful spell at Liverpool. Celtic fans may even hope the man of many clubs, who has clocked up in excess of £70 million in transfer fees during his career, may eventually decide to make Glasgow his long-term home.

But as Mowbray looks for some inspiration from Keane against the Pars to bolster his cup bid, it could be argued the manager who inflicted the latest defeat on the Celtic manager has conducted the best bit of business in the January window.

Killie boss Jimmy Calderwood is relishing the visit of Inverness Caley Thistle this weekend. However, Calderwood knows his main task is keeping his new club in the top flight and his surprise move for Scott Severin has already been described as a masterstroke.

The Scotland international will play from the start against Caley in the Cup having started on the bench against Celtic following a period of inactivity at parent club Watford.

Severin served Calderwood admirably when the pair were together at Aberdeen and his experience will prove vital during the forthcoming relegation dogfight. The money he will receive will be dwarfed by the huge figures Keane is reportedly getting from the Hoops for his brief stay in Scotland.

But if Seve, who has struggled to shine since swapping Pittodrie for Vicarage Road last summer, helps to maintain Kilmarnock's SPL status he might just safeguard the long-term future of the Ayrshire men.

The former Hearts midfielder will relish the opportunity to team up with Calderwood in the SPL again and it will be interesting to see if he quickly rediscovers his top form following a frustrating period in England.

Both Keane at Celtic and Severin at Killie should play key roles in helping to get their clubs safely through to the next round of the Cup at the expense of Dunfermline and Caley.

Aberdeen also opted to go down the route of bringing in loan players to bolster their squad, a trend that is certainly in favour across Europe. Boss Mark McGhee has landed Plymouth pair Jim Paterson and Steven MacLean on temporary deals until the end of the season.

McGhee moved to land the duo to replace Lee Miller, who moved on to Middlesbrough for £500,000, and Tommy Wright and Maurice Ross who have also recently left the club.

But the new recruits failed to inspire the Dons as they lost 1-0 to Falkirk at Pittodrie in midweek, making them one of the most unpredictable sides in Scotland. They will need to perform on Saturday as Aberdeen face a tough Cup test away at Raith Rovers, who will be boosted by the fact Miller is now plying his trade in the Championship.

Other interesting ties include two all-SPL clashes between St Johnstone and Dundee United and St Mirren and Rangers. Hibs, a good outside tip, are at home to Montrose and will be expected to progress with ease.

The other ties include Dundee up against Ayr United at Dens Park while Ross County entertain Stirling Albion in the Highlands. But, despite a number of other potentially explosive ties, the media circus will only have one place to be this weekend, as it follows Keane on his travels to see him make his Scottish Cup debut for Celtic against Dunfermline on Sunday.